關於流的簡單操作,錯在哪里? (100分)

H

HereIsMe

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• 2003-10-10

• #1

請用樓下的代碼測試,問題是:為什麼ShowMessage(S)不是'aa'?
var
Len: word;
S, str: string;
b: Byte;
begin
str := 'aa';
Len := Length(str);
FieldStream.Seek(0, soFromBeginning);
FieldStream.Write(Len, 2);
FieldStream.Write(str, Len);

FieldStream.Seek(0, soFromBeginning);
FieldStream.Read(Len, 2);
SetLength(S, Len);
if Len > 0 then begin
FieldStream.Read(S[1], Len);
FieldStream.Read(b, 1);
if not VarIsNull(S) then
ShowMessage(S);//為何這里不顯示'aa'
end;
end;

 

L

LeeChange

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GUEST, unregistred user!

• 2003-10-10

• #2

var
Len: word;
S, str: string;
b: Byte;
FieldStream: TStream;
begin
FieldStream:=TMemoryStream.Create;
str := 'aa';
Len := Length(str);
FieldStream.Seek(0, soFromBeginning);
FieldStream.Write(Len, 2);
FieldStream.Write(str[1], Len);

FieldStream.Seek(0, soFromBeginning);
FieldStream.Read(Len, 2);
SetLength(S, Len);
if Len > 0 then begin
FieldStream.Read(S[1], Len);
FieldStream.Read(b, 1);
if not VarIsNull(S) then
ShowMessage(S);//為何這里不顯示'aa'
end;
end;

 

H

HereIsMe

Unregistered / Unconfirmed

GUEST, unregistred user!

• 2003-10-10

• #3

to :LeeChange
sorry
FieldStream已經定義且已經建立.
否則這段程序是不能運行的,而不是顯示不正確了.

 

S

stargazer

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GUEST, unregistred user!

• 2003-10-10

• #4

FieldStream 是个什么东西？在哪定义的？

 

L

LeeChange

Unregistered / Unconfirmed

GUEST, unregistred user!

• 2003-10-10

• #5

var
Len: word;
S, str: string;
b: Byte;
begin
str := 'aa';
Len := Length(str);
FieldStream.Seek(0, soFromBeginning);
FieldStream.Write(Len, 2);
FieldStream.Write(str[1], Len);

FieldStream.Seek(0, soFromBeginning);
FieldStream.Read(Len, 2);
SetLength(S, Len);
if Len > 0 then begin
FieldStream.Read(S[1], Len);
FieldStream.Read(b, 1);
if not VarIsNull(S) then
ShowMessage(S);//為何這里不顯示'aa'
end;
end;

 

L

lichdr

Unregistered / Unconfirmed

GUEST, unregistred user!

• 2003-10-10

• #6

tfieldstream是文件流，系統有的。
其他也不知道。剛才是樓主發的短消息嗎。
流不是很懂啊。

 

迷

迷糊

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GUEST, unregistred user!

• 2003-10-10

• #7

如果FieldStream创建了的话上面的过程没错，可以显示aa

 

L

LeeChange

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• 2003-10-10

• #8

楼主请仔细对比咱俩的代码，并不一样，多了个[1].

 

宁

宁柯

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• 2003-10-10

• #9

LeeChange说得没有错，应该象他说的这样就可以了！

 

H

HereIsMe

Unregistered / Unconfirmed

GUEST, unregistred user!

• 2003-10-10

• #10

LeeChange, thanks.
不過為什麼沒有了給分功能了!!!

 

L

LeeChange

Unregistered / Unconfirmed

GUEST, unregistred user!

• 2003-10-10

• #11

呵呵，没有给分功能就不给了吧。[]

 

H

HereIsMe

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GUEST, unregistred user!

• 2003-10-15

• #12

thanes